Leases (Schedule of Changes in Operating Lease Liabilities) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Operating
Operating Lease, Liability	$ 306
Operating Lease Liability Assumed in Exchange for Right-of-Use Asset	142
Operating Lease, Contract Modifications Increase (Decrease)	4
Gain (Loss) on Disposition of Operating Lease Liabilities	(1)
Operating Lease, Liabilities Settled	(177)
Finance Lease, Liability Assumed in Exchange for Right-of-Use Asset	573
Finance Lease, Contract Modifications Increase (Decrease)	0
Dispositions	0
Liabilities settled	(5)
Accretion of discount	4
Ending lease liabilities (e)	572
Accretion Expense, Operating Leases	$ 13